package design_pattern;

import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;



class HashMaps {
  public static void main(String[] args) {

    Map map = new HashMap();
    map.put("a", "aaa");
    map.put("b", "bbb");
    map.put("c", "ccc");
    map.put("d", "ddd");
    map.put(null, null);
    Iterator iterator = map.keySet().iterator();
    while (iterator.hasNext()) {
      Object key = iterator.next();
      System.out.println("map.get(key) is :" + map.get(key));
    }

    Hashtable tab = new Hashtable();
    tab.put("a", "aaa");
    tab.put("b", "bbb");
    tab.put("c", "ccc");
    tab.put("d", "ddd");
    // tab.put(null, null);
    Iterator iterator_1 = tab.keySet().iterator();
    while (iterator_1.hasNext()) {
      Object key = iterator_1.next();
      System.out.println("tab.get(key) is :" + tab.get(key));
    }

    TreeMap tmp = new TreeMap();
    tmp.put("c", "ccc");
    tmp.put("a", "aaa");
    tmp.put("b", "bbb");
    tmp.put("d", "ddd");
    Iterator iterator_2 = tmp.keySet().iterator();
    while (iterator_2.hasNext()) {
      Object key = iterator_2.next();
      System.out.println("tmp.get(key) is :" + tmp.get(key));
    }
  }
}
